Such apparatuses are used for necking or grooving can bodies. For necking, a can body is reduced in diameter at one or both ends so that the diameters of the top and bottom ends of the can are made smaller.
Grooving entails inserting a cam-controlled profiled inner tool into the end of the can body and then rolling it off against an annular internally profiled outer tool so that the groove profile is imparted to the wall of the can-body end. Grooving serves for increasing the resistance to implosion of a filled can that is internally pressurized and filled hot and then cooled, so that the can interior is depressurized after cooling.
An example of an apparatus for forming a necked or grooved section at an end of a can body is shown in EP 0,772,501 (U.S. Pat. No. 5,653,138). Here two axially movable inner tools of which at least one is made to rotate, and with a shape corresponding to the necked and edged end are used with an outer shaping tool movable radially inward against the inner tools, which are mounted on separate coaxial shafts and which are mounted on their shafts so that they are braced against axial shifting. The region holding the cylindrical work piece of at least one of the inner tools has a radially effective clamping system that is pressed against the inner surface of the cylindrical body. The outer shaping tool is pressed for forming the necked or edged end against the profile of the inner tool such that the two inner tools shift axially apart. The radial displacement of the second tool is effected by a pivoted arm that is provided according to EP 0,772,501 with a follower roller that engages in a stationary cam groove. This cam drive moves the outer shaping tool drive inward toward and outward away from the common axes of the inner tools. Alternatively instead of the pivot arm it is possible to use an eccentric. The control cam determines the pivot arc, the type of movement—linear, progressive, degressive, or other—of the tool as well as the actual coordinates of the position of the movable tool, in particular the starting and ending points of the pivotal movement relative to the inner tools, which are usually rotatable but radially nonmovable and axially shiftable.
In order to accommodate variations in the workpiece reflected in the end position of the movable shaping tool, the shaping tool must be radially adjustable on the pivot arm. The cost of the mechanical parts for the pivot arm with an adjustable tool are considerable. Setting the shaping tool on the pivot arm or of the shaping tools on the pivot arms takes up quite some time.
In particular with multiple-head machines with plural shaping tools on change of the can diameter of the workpiece at least the shaping rollers must be changed in order to get the necessary geometry. The type of movement, that is for example linear progressive or degressive, as well as the control positions are not changeable. The pivot-arm movement is dictated by the mechanism even when there is no workpiece on the inner tool. Change in format requires an expensive switching of the mechanical drive.